VISUAL INFORMATION-PROCESSING AFTER SEVERE CLOSED-HEAD INJURY - EFFECTS OF FORWARD AND BACKWARD-MASKING

Three tachistoscopic tasks were employed to assess whether survivors o f severe closed head injury (CHI) exhibit a disturbance of information processing within peripheral and/or central visual pathways. Twelve s urvivors of severe CHI and 12 individually matched control subjects co mpleted a recognition threshold (no mask) task, a monoptic, forward ma sking by visual noise task (to assess processing within relatively per ipheral pathways), and a dichoptic, backward masking by pattern task ( to assess processing within central pathways). For each experimental p rocedure, the minimum exposure durations required by subjects to ident ify correctly single consonants and triple consonants were determined. Survivors of severe CHI showed deficits on all three visual tasks. Bo th groups also had higher threshold durations for the more complex sti muli (triple v single consonants), but differences in threshold were g reater in the patients with CHI. The degree of perceptual impairment e xhibited by patients with CHI was highly variable and not consistently related to injury characteristics or residual motor or speech and lan guage impariment.